Scanning probe apparatus

ABSTRACT

In a scanning probe apparatus capable of always effectively canceling an inertial force to suppress vibration even in repetitive use while replacing a sample holding table or a probe, a stage for a sample or the probe includes a drive element for moving the sample holding table and movable portions movable in a direction in which an inertial force generated during movement of the sample holding table. The stage is configured so that the drive element, the movable portions, and the sample holding table or the probe are integrally detachably mountable to a main assembly of the scanning probe apparatus.

FIELD OF THE INVENTION AND RELATED ART

The present invention relates to a scanning probe apparatus forobtaining information of a sample or effecting processing of the sampleor information recording by ordinarily utilizing a scanning probemicroscope (SPM), and a drive stage for the scanning probe apparatus.

Japanese Laid-Open Patent Application (JP-A) No. 2002-082036 hasdisclosed a scanning mechanism for an SPM capable of suppressing anoccurrence of a vibration caused by a scanning operation to permithigh-accuracy position control at high speed.

More specifically, as shown in FIG. 7, a scanning mechanism 200 includesbases 201 and 202 for drive elements (actuators), drive element holdingmember 206 and 207 provided on the bases, a drive element 203 held bythese holding members and capable of expanding and contracting in Ydirection, a drive element 204 fixed at one end of the drive element 203and capable of expanding and contracting in X direction, a drive element205 fixed at one end of the drive element 204 and capable of expandingand contracting in Z direction, and a sample stage 208 provided on oneend of the drive element 205. The drive element 205 is connected to thedrive element 204 in its center or the neighborhood of the center. Thedrive element 204 is connected to the drive element 203 in its center orthe neighborhood of the center. The drive element 203 is held by theholding members 206 and 207 in its center or the neighborhood of thecenter.

JP-A No. 2000-088983 has disclosed an SPM which includes a small-sizeand lightweight drive stage causing less occurrence of vibration evenwhen driven at high speed and is capable of obtaining a clear image athigh speed.

More specifically, FIG. 8 shows a drive stage including a supportingmember, two or more movable portions 505 and 515 supported by thesupporting member, and two drive elements 500 and 510 for driving thetwo or more movable portions. This drive stage is constituted so thatthe movable portions 505 and 515 are driven in a direction in whichinertial forces generated in the movable portions are mutually canceledduring the drive of the drive elements. In this case, each drive elementitself is moved in three directions of X, Y and Z, so that the movableportions and the drive elements can also be inclusively referred to asmovable portions.

In the SPM, a size of the apparatus varies depending on a size of asample to be observed or information to be observed. More specifically,a small drive stage can be used in a narrow field for view (scanningrange) of a small sample to be observed and a large drive stage can beused in a wide scanning range.

In the case of using an atomic force microscope (AFM) as the SPM, thesame probe can be used in common, so that a scanning stage is removedfrom a main assembly of the SPM and another scanning stage is mounted tothe SPM main assembly. Thus, only the scanning stage is replaced in somecases.

As described above, in the case of the scanning stage including themovable portions (counterweights) capable of canceling the inertialforces, when only the scanning stage is replaced, a balance with thecounterweight cannot be retained. As a result, expected cancellation ofinertial forces cannot be effected in some cases.

Particularly, in the case where an electromechanical transducer such asa piezoelectric element is used as a drive element (actuator) for thescanning stage or the counterweight, an operation performance of thedrive element is changed with use. Accordingly, when the SPM iscontinuously used after only the scanning stage is replaced,deterioration of the drive element for the counterweight progresses andon the other hand, the scanning stage is refreshed by the replacement.As a result, an amount of displacement is different between the driveelement for the counterweight and the drive element for the scanningstage, so that it is more difficult to cancel inertial forces generatedin the scanning stage.

It has been clarified that this difficulty is also true for the casewhere a probe and a drive element for effecting scanning thereof arereplaced in an SPM of the type wherein a sample is fixed and the probeis subjected to the scanning.

SUMMARY OF THE INVENTION

A principal object of the present invention is to provide a scanningprobe apparatus capable of always effectively canceling an inertialforce to suppress vibration even when the scanning probe apparatus isrepetitively used while replacing a sample holding table or a probe.

According to an aspect of the present invention, there is provided ascanning probe apparatus for obtaining information of a sample orprocessing the sample with relative movement between the sample and theapparatus, the apparatus comprising:

a probe; and

a sample stage for holding the sample,

wherein the sample stage comprises a sample holding table, a driveelement for moving the sample holding table, and a movable portionmovable in a direction in which an inertial force generated duringmovement of the sample holding table is canceled, and wherein the samplestage is detachably mountable, integrally with the sample holding table,the drive element, and the movable portion, to a main assembly of theapparatus.

According to another aspect of the present invention, there is provideda scanning probe apparatus for obtaining information of a sample orprocessing the sample with relative movement between the sample and theapparatus, the apparatus comprising:

a probe; and

a sample stage for holding the sample,

wherein the probe is provided on a drive stage comprising a probe tablefor holding the probe, a drive element for moving the probe, and amovable portion movable in a direction in which an inertial forcegenerated during movement of the sample holding table is canceled, andwherein the drive stage is detachably mountable, integrally with theprobe table, the drive element, and the movable portion, to a mainassembly of the apparatus.

According to an embodiment of the present invention, it is possible toalways effectively canceling an inertial force to suppress vibrationeven when the scanning probe apparatus is repetitively used whilereplacing the sample holding table or the probe.

These and other objects, features and advantages of the presentinvention will become more apparent upon a consideration of thefollowing description of the preferred embodiments of the presentinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view for illustrating constitution of ascanning stage in Embodiment 1 of the present invention.

FIG. 2 is a schematic view for illustrating a structure of the scanningstage in Embodiment 1.

FIG. 3 is a schematic view for illustrating a driving method of thescanning stage in Embodiment 1.

FIG. 4 is a schematic perspective view for illustrating constitution ofa scanning stage in Embodiment 2.

FIGS. 5( a) to 5(c) are schematic views for illustrating theconstitution of the scanning stage in Embodiment 2.

FIG. 6 is a schematic view for illustrating a scanning probe apparatusaccording to Embodiment 3 of the present invention.

FIG. 7 is a schematic perspective view for illustrating a conventionalscanning stage.

FIG. 8 is a schematic sectional view for illustrating an operation of aconventional scanning stage.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the present invention, as the scanning probe apparatus, it ispossible to use a scanning probe microscope (SPM).

The SPM is a scanning microscope for obtaining information of a surfaceof a sample or processing the sample by effecting scanning with a probeor the sample and is a general name of microscopes including scanningtunneling microscope (STM), atomic force microscope (AFM), (scanning)magnetic force microscope (MFM), scanning capacitance microscope (SCaM),scanning near-field optical microscope (SNOM), and scanning thermalmicroscope (SThM).

The scanning probe microscope (SPM) is capable of effecting rasterscanning of a probe and a sample relative to each other in XY directionsto obtain surface information in a desired sample region through theprobe, thus displaying the surface information on a TV monitor in amapping mode. Further, the SNOM or the like is capable of effecting fineprocessing by the action of light emitted from a tip of the probe onto amember to be processed or capable of effecting information recordingwith light. Further, it is also possible to effect fine processing orinformation recording, such as formation of projections and recesses ata sample surface.

In such an SPM, a scanning mechanism for effecting motion in Z directionby performing feedback control so that an interaction between the sampleand probe is constant also in Z direction during XY scanning. The motionin Z direction is, different from regular movement in XY directions, anirregular motion since it reflects a sample shape or sample state of thesample, but is generally referred to as a scanning operation in Zdirection. The Z direction scanning is a motion at a highest frequencyamong the scannings in XYZ directions. More specifically, the SPM has ascanning frequency of from about 0.05 Hz to about 200 Hz in X direction.A Y direction scanning frequency is about 1/(number of Y directionscanning lines). The number of Y direction scanning lines is 10-1000lines. Further, a Z direction scanning frequency is from about (Xdirection scanning frequency)×(number of pixels per one scanning line inX direction) to about 100×(X direction scanning frequency)×(number ofpixels per one scanning line in X direction).

For example, when an image of 100 pixels in X direction and 100 pixelsin Y direction is acquired in 1 sec., the X direction scanning frequencyis 100 Hz, the Y direction scanning frequency is 1 Hz, and the Zdirection scanning frequency is 10 kHz or more. Incidentally, this Zdirection scanning frequency is a currently highest scanning frequency.Most of SPMs remain at an X direction scanning frequency of aboutseveral Hz. In order to realize the above described higher frequencies,a scanning mechanism therefor is required to be not only stable againstexternal vibration but also suppressed in vibration generated by thescanning mechanism itself during an inner scanning operation.

According to an embodiment of the present invention, in a scanning probeapparatus which includes a probe and a sample stage for holding a sampleand obtains information of a sample with relative movement between thesample and the apparatus or processes the sample with relative movementbetween the sample and the apparatus,

(1) the sample stage is characterized in that it comprises a sampleholding table, a drive element for moving the sample holding table, anda movable portion movable in a direction in which an inertial forcegenerated during movement of the sample holding table is canceled, andthat the sample stage is detachably mountable, integrally with thesample holding table, the drive element, and the movable portion, to amain assembly of the apparatus, or

(2) the probe is characterized in that, it is provided on a driver stagecomprising a probe table for holding the probe, a drive element formoving the probe, and a movable portion movable in a direction in whichan inertial force generated during movement of the sample holding tableis canceled, and the drive stage is detachably mountable, integrallywith the probe table, the drive element, and the movable portion, to amain assembly of the apparatus.

Further, the scanning probe apparatus may also include both of the abovedescribed features (1) and (2).

The probe usable in the present invention may be formed of silicon,silicon nitride, tungsten, cobalt, carbon fiber, etc. A shape andmaterial for the probe may be appropriately selected depending on usesof the SPM.

The probe is provided to a cantilever of silicon or another metal and asurface of the cantilever may be coated with metal such as aluminum orplatinum.

The drive element usable in the present invention may preferably be anelectromechanical transducer such as a piezoelectric element. Thepiezoelectric element may have a cylindrical shape or a laminationshape.

The movable portion usable in the present invention may be acounterweight itself, a combination of the counterweight and the driveelement such as the electromechanical transducer for driving thecounterweight or may also be an electromechanical transducer also havingthe function as the counterweight.

The sample holding table usable in the present invention may be a memberon which the sample is mounted or a member provided with an adsorptionmeans for fixing the sample so that the sample is not moved on thesample holding table.

Further, in the present invention, it is preferable that an electricconnector of the scanning stage and an electric connector of theapparatus main assembly are connected together with mounting of thescanning stage and disconnected together with demounting of the scanningstage.

Embodiment 1

FIG. 1 is a schematic sectional view of a scanning stage used in an SPMand FIG. 2 is a schematic view for illustrating a structure of thescanning stage.

The scanning stage includes, e.g., an outer housing 1 formed of metal,as desired, and is replaceably mounted and engaged in a recess portion 2of a main assembly of the SPM. Further, as needed, the apparatus mainassembly and the scanning stage may also be fixed with a screw. Outsidea bottom supporting member 9 of the scanning stage, an electricconnector 3 is provided. At a bottom of the recess portion 2, anelectric connector 4 is provided. These electric connectors 3 and 4 areconnected when a scanner is engaged in the recess portion 2 to bemounted to the apparatus main assembly and are externally suppliedthrough a drive circuit 5 with signals for driving a scanner driveelement 500, as a drive element for a sample holding table, and acounter drive element 510.

The scanner drive element 500 is a cylindrical piezoelectric element anda circular plate-like sample holding table 505 is provided at an upper(top) portion of the drive element 500. On the other hand, the counterdrive element 510 is a cylindrical piezoelectric element having asmaller diameter than the scanner drive element 500 and a counterweight515 is provided at an upper portion of the drive element 510.

Based on X drive signal, Y drive signal, and Z drive signal outputtedfrom a control circuit 6 of the apparatus main assembly, the signals areappropriately converted into voltage signals suitable for driving thepiezoelectric elements and applied to the scanner drive element 500 andthe counter drive element 510.

The respective piezoelectric elements (drive elements) are driven in amanner as described in JP-A No. 2000-088983.

As shown in FIG. 2, the scanning stage includes two drive stagesconsisting of two cylindrical piezoelectric elements concentricallydisposed. More specifically, inside a first cylindrical piezoelectricelement 500, a second cylindrical piezoelectric element 510 isconcentrically disposed. This state is shown in FIG. 2 as an explodedview. Around the first cylindrical piezoelectric element 500, dividedfour electrodes 501 to 504 are disposed (in FIG. 2, the electrode 504 isnot shown since it is located on a backside), and at an upper portion ofthe first cylindrical piezoelectric element 500, a sample holding table505 is connected. Further, around the second cylindrical piezoelectricelement 510, divided four electrodes 511 to 514 are disposed (in FIG. 2,the electrode 514 is not shown), and at an upper portion of the secondcylindrical piezoelectric element 510, a counterweight 515 is connected.The first and second cylindrical piezoelectric elements 500 and 510 canbe bent by controlling voltages applied to opposite two electrodes (501and 503, 502 and 504, 511 and 513, or 512 and 514) so that one of thetwo electrodes is expanded and the other electrode is contracted.Further, it is also possible to expand and contrast each of thecylindrical piezoelectric elements in a long axis direction by applyingthe same voltage to the divided four electrodes. In short, the bendingand the expansion and contraction of the cylindrical piezoelectricelements 500 and 510 can be controlled by voltages.

Here, as a modified embodiment, the electrodes 501 to 504 may also beused for scanning in XY directions and another piezoelectric element maybe provided for scanning in Z direction. The Z direction scanningpiezoelectric element may, e.g., be provided above the electrodes 501 to504.

Therefore, it is possible to three-dimensionally drive the sampleholding table (movable table) 505 and the counterweight 515 disposed atthe upper (top) portions of the cylindrical piezoelectric elements.

FIG. 3 is a wiring diagram for the scanning stage in this embodiment.

By effecting wiring as shown in FIG. 3, the outer cylindricalpiezoelectric element 500 and the inner cylindrical piezoelectricelement 510 are always driven in mutually opposite directions. Abehavior of deformation of the cylindrical piezoelectric elements is thesame as in JP-A No. 2000-088983. Similarly, as in the case of FIG. 8,the cylindrical piezoelectric element 500 is bent and expanded toward anupper left direction, the cylindrical piezoelectric element 510 is bentand contracted toward a lower right direction. Gains-Ax, -Ay, and -Az ofamplifiers 520, 521 and 522 are set to cancel inertial forces withrespect to the cylindrical piezoelectric elements 500 and 510 in X, Yand Z directions, respectively. Further, these gains may desirably beadjusted to optimum values when a weight of an object to be placed on amoving table.

In this embodiment constituted as described above, the drive stage isalways driven so that inertial forces generated with respect to theouter first cylindrical piezoelectric element 500 and the inner secondcylindrical piezoelectric element 510 are canceled. As a result,movement of the center of gravity of the drive stage can be suppressedso that it is zero or a negligible level. Accordingly, it is possible toprovide a scanning stage causing less vibration even when the sampleholding table is driven at high speed.

In this embodiment, not only the scanning piezoelectric element but alsothe inertial force canceling piezoelectric element are replaceable. Morespecifically, these piezoelectric elements are fixed on the bottomsupporting member 9 and the bottom supporting member 9 is detachablymountable to the apparatus main assembly. As a result, both the scanningpiezoelectric element and the inertial force canceling piezoelectricelement are integrally replaceable.

Thus, even when the SPM is repetitively used with replacement of thesample holding table, it is possible to always cancel the inertialforces thereby to suppress vibration.

Further, when the scanning stage is provided with a cantilever and aprobe in place of the sample holding table 505, it is possible toprovide a scanning stage for the probe.

Embodiment 2

Embodiment 2 of the present invention will be described with referenceto FIGS. 4 and 5( a) to 5(c).

Referring to these figures, a scanning stage 400 includes a scanningstage holding table 401 on a main assembly side of an SPM and a driveelement supporting member 402 replaceably fixed on the scanning stageholding table 401. On the drive element supporting member 402, driveelement holding members 406 and 407 are provided so as to hold a driveelement 403. At one end of the drive element 403, a drive element 404 isfixed. At one end of the drive element 404, a drive element 505 isfixed. At the other end of the drive element 404, a counterweight member409 is fixed. At one end of the drive element 405, a sample holdingtable 408 is provided.

The drive elements 403, 404 and 405 are laminated piezoelectricelements. Further, the counterweight member 409 is also a laminatedpiezoelectric element. The drive element 405 is capable of expanding andcontracting in Z direction (first direction) and is connected to one endof the drive element 404 in its center or the neighborhood of thecenter. The counterweight member 409 has the same weight as the driveelement 405 and is connected to the other end of the drive element 404in its center or the neighborhood of the center.

The drive element 404 is capable of expanding and contracting in Ydirection (second direction) and is connected to one end of the driveelement 403 in its center or the neighborhood of the center. The driveelement 403 is capable of expanding and contracting in X direction(third direction) and is held by the drive element holding members 406and 407 in its center or the neighborhood of the center.

As described above, the supporting member 402 is engaged in the recessportion of the scanning stage holding table 401 to be detachably fixedwith a screw. As a result, the sample holding table 408 is integrallyreplaceable together with the counterweight member 409 with respect tothe scanning stage holding table 401.

In this embodiment, replaceable members are not limited to the scanningpiezoelectric element (drive element) 405 and the sample holding table408. The scanning drive element 405 and the inertial force cancelingdrive element 409 are fixed to the supporting member 402, and thesupporting member 402 is configured to be detachably mountable to thescanning stage holding table 401 on the apparatus main assembly side. Asa result, both the piezoelectric elements (drive elements) areintegrally replaceable.

In this embodiment, it is also preferable that a counterweight havingthe same weight as the sample holding table 408 is provided at a lowerportion of the drive element 405 in Z direction and is moved in adirection opposite to a movement direction of the sample holding table408. As a result, movement of the center of gravity in Z direction canbe suppressed to prevent vibration in Z direction. In this case,symmetry with respect to movement direction (direction of motion) isfurther increased, so that it is possible to provide the counterweightin all the X, Y and Z directions.

Further, it is also preferable that a counterweight having the sameweight as a total of weights of the sample holding table 408, the driveelement 405, the drive element 404, and the counterweight member 409 isprovided at an end of the drive element 403, opposite to the end atwhich the drive element 403 and the drive element 404 are connected, andis moved in a direction opposite to the movement direction of the sampleholding table 408 in X direction. As a result, movement of the center ofgravity in X direction can be suppressed to prevent vibration in Xdirection.

As described above, according to this embodiment, even when the SPM isrepetitively used with replacement of the sample holding table, it ispossible to always effectively cause the inertial forces to suppressvibration.

Further, by providing a cantilever and a probe in place of the sampleholding table 408, it is possible to provide a scanning stage for theprobe.

Embodiment 3

FIG. 6 shows a scanning probe apparatus according to this embodiment ofthe present invention.

Referring to FIG. 6, the AFM includes a frame 10 of a main assembly ofapparatus, a recess portion 11 of the apparatus main assembly, ascanning stage 12 for performing scanning of sample, a sample 13, arecess portion 14 for a drive stage of the apparatus main assembly, adrive stage 15, a cantilever 16, and a probe 17. A reference numeral 18represents a drive control circuit including a drive circuit, a controlcircuit, a detection circuit, and an image processing circuit.

In this embodiment, as the scanning stage 12, it is possible to use thescanning stage in Embodiment 1 or Embodiment 2. Further, as the drivestage 15, it is possible to use the scanning stage in Embodiment 1 orEmbodiment 2. Further, it is also possible to use the scanning stage inEmbodiment 1 or Embodiment 2 as both of the scanning stage 21 and thedrive stage 15.

In any of the above cases, when at least one of the scanning stage 12and the drive stage 15 is replaceable, the counterweight and the driveelement for driving the counterweight are configured to be integrallydetachably mountable to the apparatus main assembly together with thesample holding table or the probe.

While the invention has been described with reference to the structuresdisclosed herein, it is not confined to the details set forth and thisapplication is intended to cover such modifications or changes as maycome within the purpose of the improvements or the scope of thefollowing claims.

This application claims priority from Japanese Patent Application No.370095/2005 filed Dec. 22, 2005, which is hereby incorporated byreference.

1.-8. (canceled)
 9. A sample stage for holding a sample, comprising: adrive element for moving a sample holding table; and a movable portionmovable in a direction in which an inertial force generated duringmovement of the sample holding table is cancelled, wherein said samplestage is detachably mountable, integrally with the sample holding table,the drive element, and the movable portion, to a main assembly of anapparatus.